The overall theme ofthe CLDRC is the recognifion that reading disability, reading comprehension deficits, and attention deficit hyperactivity disorder are complex conditions that result from deficits in multiple component abilities, some of which are independent and some which are shared. In the projects within the CLDRC, these components are characterized by their genefic and developmental characteristics and their interacfion with environment. In Project IV, we will also characterize the genefic contributions to these abilifies at the molecular level. We hypothesize that the genes affecfing reading, reading comprehension, and attention will be in similar developmental pathways, and that those pathways will help define the neurodevelopmental processes involved in these conditions. Further, we expect that there will be some disfinct genetic influences on reading, reading comprehension, and attention, and that there will also be genes that have more universal effects. To identify the contribufing genes, we will extend our current association analyses to design targeted DNA sequencing approaches to identify both common and rare variants in well-characterized candidate regions. We will then test whether these same genetic variants (putative mutations) influence reading, reading comprehension and attention in geographically and ethnically diverse populations. The molecular genetic results will tie together the detailed phenotypic studies ofthe other projects to define the neurodevelopmental etiologies of learning disabilifies and then determine how they generalize across populafions. This will provide an etiological framework to describe the genetic infiuences on learning disabilities, with potenfial therapeutic and diagnostic implications. RELEVANCE (See instructions): The Genomic Analyses project will combine molecular genefic studies with the detailed data on reading, reading comprehension, and ADHD that is being obtained from twins and their families by the other Projects in the Center. Comprehensive DNA sequencing will be used to discover mutafions in genes and regulatory regions, with the overall goal of understanding the developmental processes that affect learning disorders.